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Old 04-30-2012, 01:04 PM   #11
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Originally Posted by hardluk1
Unless your willing to give up energy and velocity with a short barrel and pay 200 and 5 extra bucks to the govermant and wait for many months to see if you get there ok to own a short barreled rifle just buy a 16" barrel.

Get a 1/8 twist then as that twist will shoot 50gr up to 72 gr fine. Are you building , buying or upgradeing a rifle . You can get a good barrel for general range time shooting tight groups and hunting from AR performance with there melonite coated R5 barrels.- http://www.ar15performance.com/5_56_223
I am building I will not use it for hunting as I have a 308 for that. I will more then likely go with a 16 after what you guys say. I don't want to wait for ever but I believe if I did I will get it. I liked the short barrels I have shot. As long as I can shoot the heavier loads I don't care. I want a good all around rifle that will take anything I can feed it. You never know what we be able to get down the road.
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Old 04-30-2012, 01:59 PM   #12
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The SBR is a tool for a particular job. I'd imagine if there was the posibility of being faces w/ an extended yard shot the SBR would get left home.

The 16" is a great gen purpose length.

I have purchased a barrel from ARP and was happy.

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Old 04-30-2012, 02:07 PM   #13
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My SBR barrel is 7.5" and its a 1:9 twist which will shoot my 55-62gr perfectly , My buddy has a similar setup and his shoots dead nuts with 55 gr at 100 yards 2" groupings with cheapo steel ammo , I think is fabulous for a 7.5" barrel @ 100 yards , Im sure it would still hit within 4" at 200 yards but he only has 100 yards to shoot since the crops are starting to come up , when the crops are gone we have about 450 to shoot

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Old 04-30-2012, 02:51 PM   #14
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@ Fixer.

I'm curious, why do you feel that barrel length is porportional to twist rate?

When did you make that chart?

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Old 04-30-2012, 03:39 PM   #15
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@ Fixer.

I'm curious, why do you feel that barrel length is porportional to twist rate?

When did you make that chart?
I think I made that chart about 10 years ago. I re-made it and posted it on CGN maybe 2 years ago.

The barrel length is more of a user ability thing than a twist rate dependant thing. Its a actual use philosophy thing. A 10" SBR isnt an AT&T rifle... (reach out and touch someone). So why choose a load or twist based on that. The 1/7 twist is best used to stabilize a heavy long round at distance, BUT it also helps at close range to tighten up the keyhole effect. Its possible a 1/9 will allow a long heavy round to start a yaw just past 100 yards esp when the barrel has some wear on it. Its not a hard and fast rule, but one I keep in the back of my mind.

I use a 1/9 even with 77gr ammo, but I expect keyholes and poor performance past a certain distance.

EDIT- The reduced energy or velocity of a 10" increases that poor performance and allows it to happen at shorter distances. You can talk me out of this logic if you have supporting data saying otherwise.

Thats just me. YMMV
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Old 04-30-2012, 04:25 PM   #16
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So a 16in barrel is what I will go with. Now if I am reading right the best twist for long and short is 1/7 or 1/8? The twist is what confuses me more. I don't know why it just does. Lol.

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Old 04-30-2012, 04:38 PM   #17
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In all honesty most box ammo on the shelves are going to be 55 gr thats whats most common anyway . I personally would go 1:9 it will allow a wider use of different weights and still shoot most anything you can buy on the shelf accurately. Really its all personal preference but this would be my choice if I did it all over again .

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Old 04-30-2012, 04:38 PM   #18
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So a 16in barrel is what I will go with. Now if I am reading right the best twist for long and short is 1/7 or 1/8? The twist is what confuses me more. I don't know why it just does. Lol.
You want a twist that produces the best stabilization for the ammo you are going to shoot. You then need (or should) develop a mindset of rules that governs your use of the rifle. As in.. This is my general purpose 16" carbine. Its used for 200 yard and under ____________. Hunting, Selfdefense, Ranch work, Yot extermination...blah blah blah. You are not going to be using this 16" carbine for 800 yard prairie dog hunting nor will you be using it (wisely) as a long distance firearm between you and someone armed. All you are going to be doing is giving that guy 800 yards away a flash to aim at with his 308 and 10X scope.

So if your GPC (General Purpose Carbine) has a 1/9 twist, you should expect the best performance from a 62gr and under bullet. If it has a 1/7 twist you can expect the best performance from a 69gr and above bullet. The 1/8 will be the best of both worlds...BUT that doesnt mean you can not use a 1/9 to shoot 77gr ammo. You just need to understand what limitations that choice has. The best way to figure that out is practice with it. See what it does at 300 yards.

I choose a 1/9 since 90% of my ammo is 62 or 55 gr. I do shoot 77gr, but understand what happens when I do.

Hope this helps.
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Old 04-30-2012, 04:40 PM   #19
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So a 16in barrel is what I will go with. Now if I am reading right the best twist for long and short is 1/7 or 1/8? The twist is what confuses me more. I don't know why it just does. Lol.
Twist rate is just that one turn of the bullet ever 7" of barrel for 1:7 etc for each rate . 1:7 spins bullets faster down the tube which is needed to stabilize a heavier round like a 78 -85 gr bullet . you need lesser twist for lighter bullets
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Old 04-30-2012, 04:55 PM   #20
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The simple:

16" Barrel for general purpose use, a 1x9 x8 x7 twist will work for the most common ammo (55 and 62 grain fmjs)

55gr FMJ are the most popular (due to price and availability) ammo. Chances are this is probably what you will be shooting exclusively. x7 x8 x9 will work, with 1x9 being the most opticmal.



If you have a more specific type of ammo (tracers, 80 grain, 77 gr smks), or more specific uses, (like long distance work, or barrier penetration requirements) you may want to get a faster twist rate (1x7 or 1x8) If you want lighter, shorter varmint type bullets, consider a 1x9 or 1x12.

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